I experienced this problem today. I bought a first generation MacBook (13″ 2.0 GHz Core Duo) for my brother. It came with 1GB of memory, but after playing around with a couple of programs I realized that was a little bit short. I was running a Windows XP in Parallels, and at the same time I had a Word document open, and a couple of browser windows. The machine almost came to a stop. Not that strange since Windows XP alone was using a couple of hundred MB of memory – maybe 400 MB. And Word running in Rosetta is a beast.
Anyhow, so I had 2GB of memory in my MacBook Pro and decided to swap a memory stick from the MacBook Pro with a stick from the MacBook. Then both machines would have 1.5 GB.
When you take out the battery pack from the MacBook you’ll find a little rail which you need to remove to get to the memory banks. Three tiny screws hold it in place, and it’s shaped like an L sort of. Here’s the thing: once I was done and I had put the memory in (marveling over the engineering making it possible to get to the memory hidden inside of the computer with the help of two cute little levers), I was unable to get the battery pack back in.
It just wouldn’t seem to fit anymore. When I tried to push the battery in it insisted on going towards the center of the computer instead of fitting snuggly. Anyhow to make a long story short it turns out I hadn’t put the L shaped rail back in place correctly. On the short leg of the L there is a little piece which needs to go into a little hole in the side of the battery compartment. Apparently I had missed that hole but since the L rail is made out of flexible metal it just bent a little and I didn’t realize it was put in wrong.
Solution was to use a little screwdriver to guide the little piece on the short leg into the little hole in the compartment wall. Then the battery fit great again and everything was A-ok.
Just writing this down to save people some time should you happen to come by this by place by Google or something.